@Misc{ 
  ButGuaMar17,
  author = { Buttazzo, Giuseppe and Guarino Lo Bianco, Serena and Marini, Michele },
  title = { Sharp estimates for the anisotropic torsional rigidity and the principal frequency },
  journal = { Journal of Mathematical Analysis and Applications },
  year = { 2017 },
  doi = { http://dx.doi.org/10.1016/j.jmaa.2017.03.055 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3379/ },
  note = { cvgmt preprint}
}